1. Field of the Invention
The present invention relates to a display device which displays a three-dimensional trajectory of a machine tool.
2. Description of the Related Art
Generally, the trajectory of a representative point, such as a front end of a tool of a machine tool, represents a three-dimensional curve. Since it is not easy to calculate an error of the three-dimensional curve, i.e., the difference between a commanded trajectory and actual trajectory (or a feedback trajectory), it is difficult to intuitively know the amount of error.
In order to easily grasp the amount of error, for example, Japanese Unexamined Patent Publication (Kokai) No. 11-143514 discloses a device adapted to display a trajectory of each axis of a machine tool, wherein a positional deviation of each axis is combined, and the trajectory is indicated while a line-type or a line color is varied depending on whether or not the combined positional error exceeds a predetermined limit value.
The combined positional deviation as described above represents a delay in the actual position relative to the commanded position at a given time. In other words, the positional deviation does not represent the deviation of the actual position from a commanded trajectory. Therefore, the combined value of the positional deviation does not correctly indicate the deviation of the actual position from the commanded trajectory. Thus, it is difficult to correctly know the error of the actual three-dimensional trajectory, and it takes time to specify a problem on the trajectory and found a cause thereof.